linux-kernel - [PATCH v2 7/8] serial: qcom-geni: disable interrupts during console writes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240906131336.23625-8-johan+linaro@kernel.org>
Date: Fri,  6 Sep 2024 15:13:35 +0200
From: Johan Hovold <johan+linaro@...nel.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jirislaby@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Douglas Anderson <dianders@...omium.org>,
	Nícolas F . R . A . Prado <nfraprado@...labora.com>,
	linux-arm-msm@...r.kernel.org,
	linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Johan Hovold <johan+linaro@...nel.org>
Subject: [PATCH v2 7/8] serial: qcom-geni: disable interrupts during console writes

Disable the GENI interrupts during console writes to reduce the risk of
having interrupt handlers spinning on the port lock on other cores for
extended periods of time.

This can, for example, reduce the total amount of time spent in the
interrupt handler during boot of the x1e80100 CRD by up to a factor nine
(e.g. from 274 ms to 30 ms) while the worst case processing time drops
from 19 ms to 8 ms.

Fixes: c4f528795d1a ("tty: serial: msm_geni_serial: Add serial driver support for GENI based QUP")
Reviewed-by: Douglas Anderson <dianders@...omium.org>
Tested-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
---
 drivers/tty/serial/qcom_geni_serial.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index f8f6e9466b40..f23fd0ac3cfd 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -477,6 +477,7 @@ static void qcom_geni_serial_console_write(struct console *co, const char *s,
 {
 	struct uart_port *uport;
 	struct qcom_geni_serial_port *port;
+	u32 m_irq_en, s_irq_en;
 	bool locked = true;
 	unsigned long flags;
 
@@ -492,6 +493,11 @@ static void qcom_geni_serial_console_write(struct console *co, const char *s,
 	else
 		uart_port_lock_irqsave(uport, &flags);
 
+	m_irq_en = readl(uport->membase + SE_GENI_M_IRQ_EN);
+	s_irq_en = readl(uport->membase + SE_GENI_S_IRQ_EN);
+	writel(0, uport->membase + SE_GENI_M_IRQ_EN);
+	writel(0, uport->membase + SE_GENI_S_IRQ_EN);
+
 	if (qcom_geni_serial_main_active(uport)) {
 		/* Wait for completion or drain FIFO */
 		if (!locked || port->tx_remaining == 0)
@@ -504,6 +510,9 @@ static void qcom_geni_serial_console_write(struct console *co, const char *s,
 
 	__qcom_geni_serial_console_write(uport, s, count);
 
+	writel(m_irq_en, uport->membase + SE_GENI_M_IRQ_EN);
+	writel(s_irq_en, uport->membase + SE_GENI_S_IRQ_EN);
+
 	if (locked)
 		uart_port_unlock_irqrestore(uport, flags);
 }
-- 
2.44.2